Architecture of Lung Parenchyma

Abstract

Two essential tasks of the mammalian lung are to provide a large gas-exchanging surface and to promote both the supply of oxygen-rich air to this surface and the removal of waste gasses from it. The mammalian lung solves the problem of providing ample surface by being, in large part, an open-celled foam, and it accomplishes the supply and removal of gasses by passively changing its volume while under varying tension. Neither solution is the only one available to an organism; the exchanging surfaces of avian lungs are more similar to bundled tubes, and air is propelled through this constant-volume array by the action of peripheral sacs.